JezA;510409 Wrote: > If you spend hundreds of pounds on a Naim s/pdif lead, is it the zeros > that are more 'zero-ey' or the ones that are more 'one-like'? Do you get > more 0s with a Naim lead, or more 1s? Do they come in a different order? > Did they go to a better school? The Naim DAC purports to buffer and > re-clock the data; it doesn't retrieve the clock-signal from the data > stream, so surely if the design is any good it should work with any > vaguely decent lead, unless of course it is susceptible to other kinds > of intereference, such as RF, which would be a pity in such an expensive > product.!???!
Like you I am sceptical on how good a lead is required, but don't dismiss it entirely. The signal does need to be fully recovered from the waveform, 100% intact or else the rest of the product is a waste. If you study data transmission you will come across eye patterns ( which show the difference between one-like and zero-ey is not as distinct as you imagine. These signals are analogue! Also you are wrong about the clock / data debate. The SPDIF signal is 'manchester bi-phase coded' clock and data combined to produce a waveform. Naim need to recover the clock, for filling their buffer with perfect data. JezA;510409 Wrote: > > Also, it is unclear how the Naim DAC works. If there are 10 close but > different clocks which are switched between intermittently to keep the > buffer from over or underflowing then that itself is a form of jitter > and/or imprecision; but if those 10 clocks belong to different sampling > frequencies (ie 32, 44, 48, 96, 192, etc) then the buffer must over or > underflow at some point. If the buffer was just kept topped up over the > network such issues would not arise - why pick a clock which 'nearly' > matches the one in the s/pdif signal when the correct frequency is in > the file header!???! The IEC SPDIF specification has two clock specifications: High accuracy - bit rate is within 50 parts per million of the nominal frequency Normal accuracy - bit rate is within 1000 parts per million of the nominal frequency. If Naim chose to use Normal Accuracy as their guide, they would have the following ten clocks specified as parts per million variation from nominal: +900, +700, +500, +300, +100, -100, -300, -500, -700, -900 This would mean that for any incoming data rate their master DAC clock would be a maximum of 100 parts per million different (0.01%). This in turn converts to buffering 0.36 seconds per hour of signal played. Which is 62 kbytes for CD rate, 203 kbytes for 24bit/96kHz, 405 kbytes for 24bit/192kHz. Not exactly onerous, as they can also shift clock rates or drop bits when transmitting digital silence to the DAC. All in all quite effective. Finally - why use SPDIF, it may be flawed but there are millions to sell to (apart from most Naim CD players !!). Dave (No bias I am a Squeezebox / Linn DS user) -- DaveWr ------------------------------------------------------------------------ DaveWr's Profile: http://forums.slimdevices.com/member.php?userid=9331 View this thread: http://forums.slimdevices.com/showthread.php?t=74471 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
